Reaction Rates

What you can expect to learn from this page:

After a student completes this module, they will hopefully be able to fully understand what a second-order reaction rate is, and how it differs from a first-order reaction.

Background Summary:

A first order reaction is when one singular molecule separates into two. The reaction rate is how long it takes for the one molecule to fully separate into two parts. A second order reaction rate is the exact opposite of this. Second-order reactions are when two separate molecules collide and combine to form a singular molecule. Like in first-order reactions, a second-order reaction rate is the time is takes for two molecules to collide and react.

Lesson:

1. Count out 50 m&m's and 50 skittles.
2. Place both types of candy in a cup. Shake the cup gently and pour the candies onto a table.
3. Look at the pile of candy on the table. Observe to see if there are any m&m's that are touching (or within one centimeter) a skittle. Separate every touching m&m/skittle combination from the rest of the group.

What do the touching m&m's represent?

A. The reacted molecules

B. The unreacted molecules

C. The reaction rate

Correct answer: A

Response to B: The candies that are not touching are unreacted.

Response to C: Although the candies in this experiment are theoretically reacting, the reaction rate is indetermineable until the end.

1. Take the non-touching candies and place them back in the cup. Repeat the experiment.
2. Continue until you have only 1 or 2 candies left. Keep track of how many "unreacted" candies you have at each stage in a table like the one below.

   Stage	# unreacted
   1	100

 

Why do you think there were less reacted molecules with every throw?

A:Because the outside temperature effected the chance that the molecules would react.

B:Because the number of molecules is decreasing each time, therefor the chance they would be touching is less.

C:Because the molecules are losing energy.

Correct Answer: B

Response to A: The temperature does not effect the reaction rate in this experiment.

Response to C: The molecules are not losing energy, so the energy is not effecting whether the molecules are reacting or not.

 

 

 

 

 

 

Homework (if any):